Compositional and structural control in bone regenerative coatings

The development of a low-temperature method of producing bioactive coatings for medical implants has been shown to bypass the problems associated with high temperature processing routes, in particular the appearance of amorph ous phases and non-stoichiometric hydroxyapatite (HA), and delamination of the coating from the substrate. An electric field/aqueous solution techniqu e for producing adherent, crack-free calcium phosphate coatings on titanium and stainless steel substrates is described. The characteristics of the co ating are a function of electrode spacing, supersaturation, temperature and current and voltage conditions. Scanning electron microscopy (SEM) charact erized the surface morphology of the coatings, which were shown to be HA. T he possibility of producing a coating of carbonate-substituted HA having th e same chemical composition as bone apatite, and forming at physiological t emperatures, has also been demonstrated. The size of the microstructure dec reased and the morphology changed as the carbonate ion concentration in the calcium and phosphate ion solution increased. (C) 1999 Kluwer Academic Pub lishers.